E 1270 (OTTO) Erbium oxide, GR 99.99% Cas no 12061-16-4 - used in biomedicine. Er2O3 are varied due to their electrical, optical and photoluminescence properties. E 1270 (OTTO) Erbium oxide, GR 99.99% Cas no 12061-16-4 - used as a gate dielectric in semi conductor devices since it has a high dielectric constant and a large band gap; as a burnable neutron poison for nuclear fuel and as coloring for glasses.